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Sulfhaemoglobinaemia caused by ferrous sulfate
  1. Laith Derbas1,
  2. Mohamed Warsame1,
  3. Mohannad Abu Omar2,
  4. Yousaf Zafar1,
  5. Gregory Howell1,3
  1. 1 Internal Medicine, University of Missouri Kansas City School of Medicine, Kansas City, Missouri, USA
  2. 2 Pulmonary/Critical Care Department, University of Missouri Kansas City School of Medicine, Kansas City, Missouri, USA
  3. 3 St Luke's Hospital, Kansas City, Missouri, USA
  1. Correspondence to Dr Mohannad Abu Omar, abuomarm{at}


A 78-year-old man was referred from his primary care clinic to the emergency department due to bluish discolouration of his lips and decreased oxygen saturation on pulse oximetry. The patient was asymptomatic. Physical exam was normal except for lip cyanosis. A CT pulmonary angiogram was negative for pulmonary embolism. Arterial blood gas (ABG) analysis with co-oximetry showed low oxyhaemoglobin, normal partial pressure of oxygen and methaemoglobinaemia, but an unexplained ‘gap’ in total haemoglobin saturation. This gap was felt to be due to sulfhaemoglobinaemia. After a thorough review of his medications, ferrous sulfate was stopped which resulted in resolution in patient’s cyanosis and normalisation of his ABG after 7 weeks.

  • drugs and medicines
  • haematology (drugs and medicines)
  • adult intensive care
  • poisoning
  • emergency medicine

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  • Contributors LD and MW wrote the manuscript. MAO and Yousaf reviewed and edited the manuscript. GH approved and supervised the whole work. All authors certify that they take public responsibility for the contents, have contributed substantially to the drafting and have approved the final version.

  • Competing interests None declared.

  • Patient consent Obtained.

  • Provenance and peer review Not commissioned; externally peer reviewed.